By Toni Clarke
(Reuters) - U.S. health regulators rejected an experimental drug to treat opioid addiction made by Titan Pharmaceuticals Inc and asked for additional data showing it works, the company said.
The drug, Probuphine, is a long-acting version of buprenorphine, a drug sold by British rival Reckitt-Benckiser Group Plc under the brand names Subutex and Suboxone.
Unlike Subutex and Suboxone, which are taken daily and dissolved under the tongue, Titan's drug is implanted under the skin of the upper arm during a 10- to 15-minute office procedure and delivers a continuous supply of buprenorphine for six months.
Clinical data showed Probuphine to be more effective than placebo in curbing addiction, but an outside panel of experts to the FDA said in March that the data were not particularly robust and suggested the proposed Probuphine dose could be too low.
Even so, the panel voted 10-4 with one abstention that the drug be approved, with the proviso that Titan clarify the most effective dose and establish a strong plan to mitigate any risk of abuse. In its rejection letter, the FDA asked, among other things, for data showing the effect of higher doses of the drug.
"I'm surprised (at the FDA rejection), given the positive advisory committee vote," said Jason Napodano, an analyst at Zacks Investment Research. "I thought given the outcome of the panel, the FDA was going to approve the device."
Napodano said it was unclear whether Titan already has the data or will need to generate it through new clinical studies.
Titan's stock fell 41 percent after the expert panel's comments on March 19. The stock plunged 72 percent to $0.45 a share in early trading on Wednesday.
Titan, which announced the FDA decision shortly before midnight on Tuesday, said it was "extremely surprised and disappointed" with the agency's response. The formulation of Probuphine is consistent with recently issued FDA guidance supporting diversion and abuse-resistant drugs, the company said.
In December, Titan licensed the U.S. and Canadian rights to Probuphine to Braeburn Pharmaceuticals, a company owned by the venture capital firm Apple Tree Partners. Titan received an up-front payment of $15.75 million and would have received an upfront payment of $50 million if Probuphine had been approved.
To date, the market for buprenorphine has been dominated by Reckitt, a consumer goods company whose products range from cleaning supplies to condoms. Subutex and Suboxone generated sales of roughly $1.3 billion in 2012.
Suboxone and Subutex lost market exclusivity in 2009, and while generic competitors promptly introduced cheap copies of Subutex, they were slow to develop alternatives to Suboxone. In the meantime, Reckitt persuaded many physicians to switch from Suboxone tablets to Suboxone Film, its newer, patent-protected wafer-like strip that patients dissolve under the tongue. At the end of 2012, according to Reckitt, Suboxone Film had captured 64 percent of the market.
Earlier this year, the FDA approved generic versions of Suboxone tablets from Amneal Pharmaceuticals LLC and Actavis Inc.
(Reporting By Toni Clarke in Washington; editing by John Wallace)